The present invention relates generally to aircraft weapons stores, and more particularly, to an apparatus and method for enhancing aircraft weapons separation from an open weapons bay during flight.
Depending on configuration and application, military aircraft will sometimes carry weapons to be discharged during flight within one or more cavities, commonly known as weapons bays. The weapons bays usually include a pair of doors which are opened only when release of the weapon stores is anticipated. During the remainder of the aircraft flight, the weapons bay doors are closed, presenting a smooth surface to enhance aerodynamic performance as well as other characteristics, such as stealthiness, for example.
While carrying weapons or stores in a normally closed weapons bay has many advantages, a known disadvantage is that the bay can negatively influence weapons release. Indeed, depending on aircraft configuration and speed, the weapon might actually pitch up and fly back toward the aircraft after release. The physical dimensions of the weapons bay are a primary contributor to this problem. More specifically, it is known that shallow bays or cavities, generally defined as having a length to height ratio of 10 or more, are far more likely to induce this type of undesirable weapons release behavior than deep bays or cavities, which are generally defined as having a length to height ratio of 4 or less. This is because the flowfield occurring in the shallow bay when opened produces a strong back to front pressure gradient within the cavity. This pressure gradient tends to push the tail of the weapon out into the airstream and may simultaneously tend to pull the nose of the weapon up towards the aircraft. Conversely, the pressure gradient produced on the ceiling of the deep bay, is characterized by a low gradient pressure profile. This is an advantage because the low pressure gradient profile tends to keep the weapon from pitching. This encourages a flatter, more even weapon separation. As weapons decrease in size, the undesirable effects of the weapons bay flowfield are magnified. Since a trend in weapons development is to make weapons stores much smaller, this problem is growing.
One way of alleviating the weapons separation problem associated with weapons bay configuration would be to convert a shallow weapons bay to a deep bay by physically altering its dimensions. While this method can perhaps be utilized on some aircraft, the dimensions of the weapons bay are usually determined in part by the size and shape of the aircraft and as a result often can't be altered to the extent necessary to effect the desired change. Further, there are competing considerations to be taken into account when considering this approach. More specifically, while deep bays, by their nature, tend to enhance weapons separation, they also display high levels of damaging acoustic resonance which causes high pressure, high frequency fluctuating acoustic loads. This acoustic resonance can be strong enough to damage the aircraft or its systems. Thus, converting a shallow bay to a deep bay in order to enhance weapons separation may result in a disadvantageous increase in damage to the aircraft itself.
Another solution is perhaps found by ejecting the weapon out of the weapons bay more vigorously. This could be accomplished, for example, by increasing weapons ejector force while increasing the nose down pitching moment of the weapon. This is oftentimes undesirable because imparting higher ejection forces would necessitate a stronger aircraft and weapon structure, increasing weight, cost and complexity. Moreover, this could result in undesirable weapons launch effects such as loss of control of a guided weapon and loss of boresight correlation with the resulting loss of a target lock-on, as the weapon is forcibly ejected.
Other attempts to reduce the undesirable shallow weapons bay separation characteristics are found, for example, in U.S. Pat. Nos. 4,863,118 and 5,018,688 both to Stallings Jr. et al. In the '118 patent, hollow pipes are placed on the ceiling of the weapons bay. In the '688 patent, a porous slab is placed adjacent the ceiling of the weapons bay. In each, the apparatus placed on the ceiling was intended to passively induce a flow of air from the back of the weapons bay to the front. These patents both represent an attempt to alleviate the high pressure gradient typically found in shallow weapons bays by passively directing a flow of air from the high pressure area in the back of the bay to the lower pressure area in the front of the bay. While moderately successful, these techniques do not outweigh the increased cost, complexity and weight attendant with their incorporation into an aircraft.
Yet another attempt is found by the placement of a spoiler at the forward edge of the weapons bay. While spoilers have some positive effect on weapons separation, a disadvantage is that spoilers often don't provide enough of the desirable nose down pitching moment for some weapon and aircraft combinations and thus are sometimes inadequate to effect the desired weapons separation.
A need exists therefore for an improved method and apparatus for actively enhancing aircraft weapon separation from an open aircraft weapons bay.
It is therefore a primary object of the present invention to provide a method and apparatus for actively enhancing aircraft weapon separation overcoming the limitations and disadvantages of the prior art.
It is another object of the present invention to provide a method and apparatus for actively enhancing aircraft weapon separation rendering assured weapons release during flight.
It is another object of the present invention to provide a method and apparatus for actively enhancing aircraft weapon separation which can be readily incorporated into existing aircraft structures.
It is still another object of the present invention to provide a method and apparatus for actively enhancing aircraft weapon separation which can be utilized on a wide variety of aircraft and weaponry.
These and other objects of the invention will become apparent as the description of the representative embodiments proceeds.